tetracycline and calcium-phosphate--monobasic--anhydrous

The aim of this study was to investigate the adsorption and desorption kinetics of antibiotics to microporous bioceramics fabricated by a novel low temperature 3D powder direct printing process. The adsorption of vancomycin, ofloxacin and tetracycline onto hydroxyapatite, brushite and monetite showed a linear correlation with the drug concentration in the immersion solution, whereas a non-linear relationship was found between the immersion time and the amount of adsorbed drug. Differences in the total amount of adsorbed drugs were correlated to the specific surface areas of the matrices, which varied between 2.4-13.1 m(2)/g. Normalised drug loadings were found to be in the range of 1.5-1.8 mg/m(2) for vancomycin and ofloxacin, whereas higher loads of up to 5-7 mg/m(2) were obtained for tetracycline. Vancomycin and ofloxacin were rapidly released into PBS buffer within 1-2 days, while tetracycline showed a much slower release rate of approximately 25% after 5 days of immersion. Additional polymer impregnation of the drug loaded matrix with PLA/PGA polymer solutions enabled the release kinetics to be delayed such that sustained release was achieved in polymer ceramic biocomposites.

Topics: Adsorption; Anti-Bacterial Agents; Biocompatible Materials; Calcium Phosphates; Chemistry, Pharmaceutical; Drug Carriers; Drug Compounding; Drug Implants; Durapatite; Kinetics; Models, Chemical; Ofloxacin; Polyesters; Polyglycolic Acid; Porosity; Powders; Solubility; Surface Properties; Technology, Pharmaceutical; Temperature; Tetracycline; Vancomycin

Topics: Calcium Phosphates; Cell Division; Cell Line; Cell Line, Tumor; Ecdysone; Genes, Tumor Suppressor; Genetic Techniques; Humans; Liposomes; Models, Biological; Plasmids; Receptors, Estrogen; Recombinant Fusion Proteins; Tetracycline; Transfection

Calcium phosphate cements are used for bone defect filling and they may also be used as delivery systems for active agents. The physicochemical behaviour of an ionic cement, with a final composition of hydroxyapatite, containing tetracycline hydrochloride was investigated. Chemical characterisation, X-ray diffraction analysis, compressive strength and tensile strength were performed. It is known that the antibiotic can be adsorbed on calcium phosphate compounds and the presence of chloride ions can strongly influence the behaviour of the cement. Adding more than 1% (w/w) of 95% pure tetracycline hydrochloride in the solid phase led to a cement with poor mechanical properties, but which, in addition to hydroxyapatite, contained residual starting reagents. For this reason, experiments were also performed with tetracycline previously treated with a calcium sulphate solution. Using a treated tetracycline, it was possible to introduce at least 7% (w/w) of active ingredient whilst still allowing the reaction to proceed to completion i.e. the formation of hydroxyapatite with good mechanical properties. Therefore, treating the tetracycline HCI with calcium sulphate solution prior to reaction conserved the activity of the antibiotic, limited the influence of the antibiotic on the cement evolution and retained the physical properties of the cement.

Topics: Bone Cements; Calcium Phosphates; Materials Testing; Microscopy, Electron, Scanning; Tetracycline; X-Ray Diffraction

Gene transfer into neurons both in vivo and in vitro may aid in understanding of gene regulation and function in nerve cells. Especially desirable is ability to control the gene expression. In this study we developed conditions for transfection of hippocampal dentate gyrus neurons in dissociated cultures in vitro by calcium-phosphate method. Furthermore, we describe an effective use of tetracycline responsive gene promoter (Tet-On) system for the controlled and very efficient expression of transfected genes. Under optimal conditions as established in this study, efficiency of transfection of neurons with green fluorescent protein (GFP) driven by constitutive cytomegalovirus (CMV) early promoter reached 2.7%. With tetracycline responsive promoter percentage of GFP-positive neurons raised in the presence of tetracycline analog, doxycycline up to 20%. Application of the Tet-On system resulted in almost 10-fold induction of GFP expression.

Topics: Animals; Anti-Bacterial Agents; Calcium Phosphates; Cells, Cultured; Cytomegalovirus; Dentate Gyrus; Doxycycline; Gene Expression; Gene Expression Regulation; Green Fluorescent Proteins; Indicators and Reagents; Luminescent Proteins; Neurons; Promoter Regions, Genetic; Rats; Tetracycline; Transfection

Implant stabilization by biologic ingrowth into a porous surface offers a durable method of prosthetic fixation. These systems, however, lack the immediate stability offered by the use of acrylic bone cement. The interface strength of porous coated Co--Cr--Mo in a canine model does not approach that of acrylic bone cement until two weeks postoperatively. It is expected that this would be a minimum time period in clinical applications. Both chemical and electrical means have been advocated as methods to affect tissue ingrowth. A study using a canine model was undertaken to determine tissue ingrowth rates utilizing examples of these two methods: (1) impregnation of the porous structures with tricalcium phosphate powder (TCP); or (2) the application of an electrical stimulator to the implant with the implant itself serving as the cathode. Ten implants were coated with TCP, two each at weekly intervals from 1 to 5 weeks. Plain porous rods were likewise implanted, serving as the controls. While histology did reveal a slightly more dense bony structure, the interface bond strength was not affected by TCP. Electrical stimulation of the implant was similarly investigated with an additional time period of 10 weeks. Compared to the controls, the electrically stimulated implants reveal no statistically demonstratable difference in interface strength. Histologic specimens indicate larger areas of calcification than are observed in the controls.

Topics: Animals; Bone and Bones; Calcium Phosphates; Dogs; Drug Implants; Electric Stimulation; Surface Properties; Tetracycline; Time Factors

Topics: Calcium Phosphates; Durapatite; Humans; Hydrogen Peroxide; Hydroxyapatites; Models, Biological; Tetracycline; Tooth Bleaching; Tooth Discoloration